Rheostat



Oct. 23, 1923.

R, R. DUNLOP RHEOS TAT Filed May 27. 1921 Patented Oct. 23, 1923.

UNITED STATES PATENT OFFICE.

ROBERT R. DUNLOP, OF COLUMBUS, OHIO, ASSIGNOR TO THE JEFFREY MANUFACTUR- I ING COMPANY, OF COLUMBUS, OHIO, A CORPORATION OF OHIO.

RHEOSTAT.

Apucauon mea my 27, 1921'. serial. No. 473,025.

To all whom it may concern.'

Be it known that I, ROBERT R. DUNLOP, a citizen of the United States. residing at Columbus` in the county .of Franklin and State of Ohio, have invented certain new and useful Improvements in Rheostats, of which the following is a specification, reference being had therein to the accompanying drawing.

The present invention relatesto certain new and useful improvements in rheostats of the class composed of a plurality of re sistance grids supported inV spaced relation to each otheran arranged in convenient l5 series for inclusion in the circuits of electric locomotives, traction cars, and similar devices.

In grid resistances of the type commonly used on electric locomotives, the changes of temperature due to the variations of the electric current flowing through the resistance elements, produces alternate expansion and contraction of the parts which tend to loosen their contacts and impair the electrical connections between adjacent grids.

It is the especial object of this invention to provide a rheostat of the class described with supporting devices adapted to adjustment whereby the contact between adjacent grids may be conveniently restored after it has become loosened in service.

The devices by which I attain this object are fully set forth in the following specification and illustrated in the accompanying drawings of which Fig. 1 is a plan view partly in section of a rheostat provided with the devices of my invention. i

Fig. 2 is an end elevation of the devices 0 illustrated in Fig. 1.

Fig. 3 is a sectional view taken along the line III-III of Fig. 1.

Fig. 4 is a cross sectional view taken along the line IV-IV of Fig. 1.

5 Like numerals refer to similar parts in the several figures.

As shown in the drawings my improved rheostat comprises a plurality of resistance grids 1 arranged side by side between the end plates 2 and 3. On the end plates 2 and 3 are formed bosses 4 and 5 provided with apertures t-hrou h which extend the rods 6 fitted with nuts by which the plates 2 and 3 and the grids 1 are clamped together.

The rods 6 are insulated from the end plates 2 and 3 and the grids 1 by tubes 8 and washers 9 composed of mica or other suitable non-combustible insulating material. Arranged upon the tubes 8 between adjacent grids are spacing washers 10 and 11 which hold said grids in spaced relation with each other. The washers 10 are composed of suitable conducting material and form electrical connections between adjacent grids, while the washers 11 are composed of suitable insulating material and serve to electrically separate adjacent' grids from each other. 'I he arrangement of these washers is such that the grids of the resistance are connected into vseries of groups suitable to afford the desired resistance.

Formed on the end plates 2 and 3 are attachment lugs 12 having apertures through which extend the attachment bolts 13 by which said end plates are securely attached to the floor plate 14, or other suitable part of the structure, of the locomotive.

Formed on certain of the spacing washers 10 are terminal connectors 15 by which the conductors 16 of the locomotive circuits are connected to the rheostat in the manner well understood in the art.

The frequent changes of temperature, due to the variations of the electric current through the resistance elements of the rheostat, produce alternate expansion and contraction of t-he parts which tends to loosen their cont-acts and impair the electrical connection between adjacent grids. that such contacts may be conveniently restored, I have provided the sleeves 17 which are slidable upon the insulating tubes 8 and are screw threaded into apertures of the end frame 2 concentric with the rods 6. Each of the sleeves 17 is provided with a hexagonal head 18 adapted to be engaged by a suitable wrench by which said sleeves may be screwed outwardly to cause them to press against the insulating washers 19 with suiiicient force to restore the contacts between adjacent grids.

As heretofore constructed it has/been necessary, when the grids became loose, to remove the rheostat from the locomotive and adjust the nuts 7 upon the rods 6. When so adjusted the nuts 7 press against the ends of the insulating tubes 8 tending to com-v press them longitudinally and produce In ordercracks Which materiallyv reduced their insulating value. The removal of the rhesstat from the locomotive also entailed such an amount of labor that adjustments were commonly deferred until serious injury had been caused by local heating at the contact between the grids. By the devices above described longitudinal pressure upon the insulating tubes 8 has been entirely eliminated and the adjustments necessary to restore contact between loosened grids may be eil'ected with a minimum of effort and without removing the rheostat from the'locomotive.

lllhat- I claim is:

l. In a rheostat, the combination Witha rigid frame comprising end plates joined together by rods, a plurality of resistance grids supported upon and insulated from said rods, and devices adjustable relative to said end plates longitudinally of said rods to clamp said grids in operative relation to each other.

2. In a rheostat, the combination with a rigid frame comprising end plates joined together by rods, a plurality of resistance grids supported upon and insulated from said rods with sleeves upon said rods and adjustable longitudinally thereof relative to said end plates to clamp said grids in operative relation to each other.

3. In a rheostat, the combination with a rigid frame comprising end plates joined together by rods, a plurality of resistance grids supported upon and insulated :trom said rods, sleeves rotatable about said rods and screw threaded into apertures of said end plates adapted to clamp said grids in operative relation with each other.

e. In a rheostat, the combination with ay rigid frame comprising end plates joinedl together by rods, insulating sleeves upon the rods, a plurality of resistance rgrids supported upon said insulating sleeves, and sleeves concentric with said insulating sleeve and adjustable longitudinally thereof tov clamp said grids in operative relation to each other.

5. In a rheostat, the combination with a rigid frame comprising end plates joined together by rods, insulating sleeves upon the rods, a plurality of resistance grids supported by the insulating sleeves, sleeves rotatable about said insulating sleeves and screw threaded into apertures of said end plate adapted to clamp said grids in operative relation with each other.

G. In a rheostat, the combination with a rigid frame comprising end plates, rods extending through apertures in the end plates and insulated therefrom, means u on the rods for holding the end lates in Xed relation to each other, insu ating sleeves surrounding the rods, a plurality of resistance grids supported upon the insulating sleeves, and clamping devices upon the insulatin sleeves and adjustable longitudinally thereot to clamp the resistance grid in operative relation With each other.

7. In a rheostat. the combination with a rigid frame comprising end plates, rods extending through apertures in said plates and insulated therefrom, means upon the rods for holding the end plates in fixed relation to each other, insulating sleeves surrounding the rods and extending through the apertures in the end plate, and clamping del vices upon the insulating sleeves and adjustable longitudinally thereof to clamp the resistance grids in operative relation to each other.

8. In a rheostat, the combination with a rigid frame comprising end plates, rods extending through apertures in the end plates and insulated therefrom, means u on the rod for holding the end plate in xed relation to eachother, insulating sleeves surrounding the rods and extending through the apertures of the end plates, sleeves rotatable about said insulating sleeves and screw threaded into apertures of said end plates adapted to clamp said grids in operative relation to each other.

9. In a rheostat, the combination with supporting plates secured in fixed relation to each other, a plurality of resistance grids supported by and between said end plates and insulated therefrom, and means. adjustable relative to said end plates to clamp said grids in operative relation to each other.

10. In a rheostat, the combination with a supporting frame, of a plurality of resistance grids supported by and insulated from said frame, and devices adjustable relative t0 said frame to clamp said grids in operative relation to each other.

In testimony whereof, I afiix my signature.

ROBERT R. DUNLOP. 

